Marking device for torque applying tool

ABSTRACT

A marking device operable in conjunction with a tool of the type for applying a predetermined torque to a rotatable fastening member to mark the fastening member for indicating that the predetermined torque has been achieved. The tool torques the fastening member through a socket member carried by a rotatable work spindle which, in turn, is driven by a fluid motor. The marking device, which is adapted to be carried by the tool or to be mounted remotely therefrom, comprises a housing having a piston adapted to forcibly eject a marking agent either through a tube extending through the interior of the spindle to mark the fastening member, or through a tube mounted externally of the tool to mark the article carrying the fastener. The marking device is operable to mark the fastening member or the article in response to a pressure fluid signal generated by the torque applying tool upon the predetermined torque being applied to the fastening member.

United States Patent 1 Peterson 1 1 MARKING DEVICE FOR TORQUE APPLYING TOOL [75] inventor: Rudolph G. Peterson, Detroit, Mich.

{73] Assignee: Carco, Inc., Detroit, Mich.

[22] Filed: May 27, 1971 {21] Appl, No.: 147,456

[52] US. Cl. 81/525 {51] Int. Cl. B251) {58] Field of Search 8i/52.4, 52.5, 53

[56] References Cited UNITED STATES PATENTS 3,389,623 6/1968 Gill 31/523 3,661,046 5/l972 Lesner 81/525 3,523,471 8/1970 Lance 81/525 3,009,37l l l/l961 Hines et a] 1. 81/53 R 3,693,433 9;1972 Palmer et 81 81/52 X Primary Examiner-James L. Jones, Jr. Attorney, Agent, or Firm-Hauke, Gifford, Patalidis & Dumont [45] Apr. 9, 1974 {57} ABSTRACT A marking device operable in conjunction with a tool of the type for applying a predetermined torque to a rotatable fastening member to mark the fastening member for indicating that the predetermined torque has been achieved. The tool torques the fastening member through a socket member carried by a rotatable work spindle which, in turn, is driven by a fluid motor. The marking device, which is adapted to be carried by the tool or to be mounted remotely therefrom, comprises a housing having a piston adapted to forcibly eject a marking agent either through a tube extending through the interior of the spindle to mark the fastening member, or through a tube mounted externally of the tool to mark the article carrying the fastener. The marking device is operable to mark the fastening member or the article in response to a pressure fluid signal generated by the torque applying tool upon the predetermined torque being applied to the fastening member.

7 Claims, 19 Drawing Figures PATENTEB 9 974 SHEET 1 [IF 4 Q\ \N Q a? INVENTOF? RUO 0L PH 6. psrmsom A from eys PATENTEBAPR 9 1914 3802.301

- sum 2 or 4 [/3 p f 7 H: 5 L/ZB/ I84 5 //z no M I w ,3, Y lv #5 A M n A; la e $4 1 13 Fig- 7 fi #v VENTOR RUDOLPH a. PETERSON BY fi PAIENTEHAPR aim 3,802,301

SHEET 3 BF 4 INVENTOI? lg RUDOLPH a. PETERSON /9 BY rromeys MARKING DEVICE FOR TORQUE APPLYING TOOL BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to a tool for applying a predetermined torque to a rotatable fastening member and particularly to means for marking the member to indicate the completed application of the predetermined torque.

II. Description of the Prior Art It is a recognized fact that to achieve a maximum efficiency for fasteners, such as a bolt and nut assembly or a threaded fastener engaged in a threaded bore the nut must be tightened down on the bolt or the fastener must be engaged in the bore to such an extent that a predetermined minimum tension is exerted on the bolt or fastener shank. This minimum tension may be exceeded, but it must be at least reached for best results. One method, which has been commonly employed to insure the attainment of the predetermined tension or preload of the bolt shank, is a method which involves determining the torque which is required to achieve the desired tension, then once having predetermined the torque for a particular size bolt, each nut is tightened to this predetermined torque.

Pneumatically operated tools, such as nut runners, are ideally suited for such applications as the not runner can repetitively and accurately apply a predeter mined torque to the nut. In using nut runners or the like for applying a predetermined torque to bolts, nuts and the like in mechanical assemblies, it is desirabie to apply a mark to each bolt andlor nut which has been tightened so that an assembler and/or an inspector can thus ascertain whether any of the bolts or nuts have been missed and thus save time by eliminating the retightening of bolts or nuts which are already sufficiently tight. Typical prior art torque wrenches or not runners are adapted to apply a mark, such as ink or paint, simultaneously with the engagement with the bolt or nut. By this technique, however, the bolt or not may be improperly marked, that is, the bolt or nut will be marked even if the tightening operation is interrupted prior to completion of full torque. Thus, the desired result of marking the nut or bolt to indicate whether a certain torque has been applied is not achieved.

SUMMARY OF THE INVENTION The present invention, which will be subsequently described in greater detail, comprises a marking device operable in conjunction with a torque applying tool of the type which delivers a predetermined torque to a rotatabie fastening member, such as a bolt or not, wherein the tool generates a signal, such as a fluid pressure, pneumatic, mechanical or electrical signal, which is indicative of a predetermined torque having been delivered to the fastening member, while the marking device in response to the signal marks the member with a suitable marking agent only upon the completed application of the predetermined torque.

It is therefore an object of the present invention to provide a marking device adapted to mark a rotatable fastening member only after a predetermined torque has been delivered to the fastening member.

Gther objects, advantages, and applications of the present invention will become apparent to those skilled in the art of such marking devices when the accompa' nying description of several examples of the best modes contemplated for practicing the invention is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and in which:

FIG. I is a side elevational view of a right angle nut runner tool including a marking device of the present invention;

FIG. 2 is a top plane elevational view of the nut runner tool shown in FIG. 1;

FIG. 3 is a fragmentary cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary cross-sectional view taken along line 44 of FIG. 3;

FIG. 5 is a fragmentary cross-sectional view taken along line 55 of FIG. I illustrating the marking de vice of FIG. I in a non-operative position;

FIG. 6 is a cross-sectional view similar to FIG. 5 but illustrating the marking device in an operative position;

FIG. 7 is a fragmentary cross-sectional view taken along line 7'! of FIG. 5 illustrating the marking device in a non-operative position;

FIG. 8 is a cross-sectional view similar to the marking device illustrated in FIG. 7 but shown in an operative position;

FIG. 9 is a fragmentary cross sectional view of the marking device as seen generally along line 99 of FIG. 5;

FIG. 10 is a fragmentary side elevational view of a right angle nut runner with a marking device of the present invention mounted externally of the housing of the nut runner and adjacent the front portion thereof;

FIG. 11 is a fragmentary side elevational view of an in-line nut runner with the ejecting end of a marking device mounted externally of the housing of the nut runner and adjacent the front portion thereof;

FIG. 12 is a side elevational view of the marking device illustrated in FIG. I and shown as being remotely mounted from the nut runner;

FIG. 13 is a fragmentary, partially sectioned side elevational view of a modified marking device mounted rearwardly of the handle portion of a nut runner;

FIG. 14 is a fragmentary, partially sectioned top elevational view of the modified marking device shown in FIG. 13'.

FIG. 15 is a crosssectional view of the modified marking device taken along line 15-15 of FIG. 13;

FIG. 16 is a cross-sectional view of the modified marking device taken along line 16-16 of FIG. 15;

FIG. 17 is a fragmentary, partially sectioned view of the modified marking device shown in FIG. 14 and illustrated in a different operative position;

FIG. 18 is a cross-sectional view of the modified marking device taken along line 18-48 of FIG. 16; and

FIG. 19 is a cross-sectional view of the modified marking device taken along line 19-19 of FIG. 13.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, a torque applying tool,

such as a pneumatic, right angle nut runner 10, is illustrated in FIGS. 1 and 2 as comprising an elongated cylindrical housing 11 including a motor portion 12, a handle portion 13 of a reduced diameter, and a front portion 14 carrying a rotatable spindle 15 (FIG. I) of the type adapted to be connected to a conventional wrench socket 16 for driving nuts, bolts and the like. A motor 17, which may be of any conventional type of fluid motor such as a rotary vane air motor, is mounted in the motor portion 12 for driving the spindle 15 by means of a shaft 18 and a bevel gear arrangement 19. The shaft 18 and the spindle 15 are both supported by suitable bearings, such as indicated by the numerals 20 and 21. A marking device 22, which will be described in greater detail hereinafter, is mounted on top of the motor portion 12 of the nut runner 10, however, as will be likewise described hereinafter in an alternate embodiment, the marking device 22 may be mounted rearwardly of the handle portion 13 or mounted remotely from the nut runner l0.

Compressed air for driving the fluid motor 17 is supplied through an air hose 23 coupled at the rear of the handle portion 13 to the nut runner l0 and flows through a suitable inlet screen 24 disposed in a passageway 25 (see FIG. 3) which, in turn, comprises a series of passages that lead to the fluid motor 17. Still referring to FIG. 3, an inlet passage 26 of the passageway 25 communicates with a double diameter valve chamber 27 defined by a bushing 28 fixed in one end of a bore 29 and extending across the housing 11, and by an air regulator 30 closing the other end of the bore 29. The air regulator 30 includes an inner cup-like member 31 forming an enlarged end of the valve chamber 27 and a shank portion 33 of a reduced diameter which, in turn, is received in a hollow plug 32 screwed into the bore 29. The inner cupJike member 31 is restrained against unintended movement by means of an O-ring 34 encircling the shank portion 33 and recessed on the inner end of the plug 32.

An inlet port 36, formed in the wall of the cup-like member 31, serves to connect the inlet passage 26 and the chamber 27, while the volume of air admitted into the chamber 27 is governed by rotatably adjusting the position of the member 31 so that it can vary the effective size of the inlet port 36, the adjustment being facilitated by a screwdriver slot 38 which is easily accessible at the outer end of the shank portion 33. Assuming a load of established value, the operator may thus vary the power of the motor 17 and the spindle speed to suit the application of the nut runner 10.

A throttle valve 40 is received in chamber 27 and has a stem 41 projecting out through the bushing 28, while an inner end of the throttle valve 40 is enlarged relative to the stem 41 and is further provided with an annular flange 44 on one side of which is mounted an annular seal 46, which, in turn, is engageable with the inner end of the bushing 28. The other side of the flange 44 is seated on a compression spring 48 and is biased between the flange 44 and member 31 so as to hold the throttle 40 in a normally closed position. The throttle valve 40 is provided with a graduated intermediate portion 49 which is tapered from an enlarged portion 42 of the throttle valve 40 to its stem 41 for the purpose of effectively minimizing the initial pressure surge of air supplied to the motor 17.

To actuate the motor 17, a hand lever 50, pivotally supported on the housing 11 rearwardly of the marking device 22 and engaging the outer projecting end of the stem 41, is compressed to unseat the throttle valve 40, whereupon air enters chamber 27 through the inlet port 36 to pass through an outlet port 52 and the bushing 28, communicating with an inlet passage 54 to a normally opened shut-off control valve 56 and therethrough to an outlet passage 58 (FIG. 4) to the motor 17.

Still referring to FIG. 4, a bore 60 extending across the housing 11 transversely of the bore 29 receives a sleeve 61 having an end extension 62 and an outlet passage 64 disposed radially outwardly of a circular compartment 63, so as to connect a chamber 65 with an outlet 66, which is suitably threaded to receive a fluid coupling such as at 67. The sleeve 61 has an open inner end adapted to abut a coaxially aligned hollow plug 68 screwed into the opposite end of the bore 60. The sleeve 61 is rigidly fixed in position by any suitable means, such as by a press-fit.

For automatically shutting off air flow to the motor 17, a valve plunger or spool 69 is received in the chamber 65, defined by the inner surface of the sleeve 61, for reciprocating movement between open and closed positions, respectively at the left and right ends of the chamber 65 as viewed in FIG. 4. The end extension 62 of the sleeve 61 and the inner end of the plug 68 provide seats for the spool 69 respectively in its open and closed positions. The spool 69 is illustrated as being normally held open in its left hand position by a coil spring 70, having one end bearing against the bottom of a cup-shaped cavity 71 in the spool 69, while the opposite end of the spring is seated within a threaded bore 72 extending through the plug 68.

So that the spool 69 is responsive to variations in the motor operating pressure, which are a function of the output force of the motor 17 and in this way is responsive to a predetermined level of torque being reached, passages in communication with the outlet passage 58 are provided for continually directing compressed air against the spool 69 to provide a force in opposition to the spring force when the spool 69 is in its opened position as shown in FIG. 4. More specifically, a passage 73 is shown as extending diametrically through a reduced intermediate portion 74 of the spool 69 and another passage 75 extends from passage 73 axially through the left hand end of the spool as viewed in FIG. 4 to provide internal passage means of a generally T-shaped cross section. Passages 73 and 75 are in communication with an outlet port 76 in the sleeve 69, which connects to the outlet passage 58 leading to the motor 17 when the spool 69 is in its opened position.

Still referring to FIG. 4, the compartment 63, formed in the extension end 62, is of a circular cross section and is adapted to receive an annular extension 77 of a reduced diameter formed at the left end of the spool 69 and surrounding the axial passageway 75. The compartment 63 and the annular extension 77 are dimensioned to provide a preselected clearance between the spool 69 and the extension end 62 of the sleeve 61. This clearance preferably is maintained by an O-ring 78 retained in a groove 79 around the extension 77 to provide a fluid-tight seal around the compartment 63 when the spool 69 is in its open position as shown in FIG. 4. Thus, the end of the spool extension 77 provides a pres sure sensing surface 80 which is in communication with the outlet passage 58 when the spool 69 is in its open position, the area of the pressure sensing surface 80 being relatively small with respect to the area of the annular end surface 81 of the spool 69 surrounding the extension 77.

To provide a torque control which is highly sensitive to variations in the output force or torque of the motor 17 as indicated by a change in the static pressure in the outlet passage 58, a drop in the air supply pressure at the inlet of the motor 17 is intentionally created across the spool 69. For this purpose, a restricted port or orifice 82 is formed in the sleeve 61. lt will be apparent that for a given size air motor and a given minimum supply air pressure, the torque at which shut-off auto matically takes place is determined by the force of the spring 70. To produce the shut-off at a desired maximum torque value, an adjustment member 83 is provided for precisely varying the spring force exerted on the spool 69. Member 83 is provided with an aperture 84 which serves to vent air trapped behind the spool 69 when the same is snapped closed, that is, when the spool 69 is moved to close communication between the passages 54 and 58.

Upon movement of the spool 69 to a shut-off position, air from the supply pressure line enters into the chamber 65 to the left of the spool 69 by means of inlet passage 54, a slot 92 and an orifice 94. By virtue of this construction, inlet air will be directed to the outlet 66 upon a movement of the spooi 69 into its shut-off position, thereby sensing the condition of the tool and automatically providing a fluid signal to the outlet 66, which signal is indicative of the completed tool operation, that is, that a predetermined amount of torque has been delivered to the nut or bolt through the spindle 15.

Upon reaching the preset shut-off torque, the pressure acting upon the small pressure sensing n'face 80 of the extension 77 within the compa rtrnent 63 reaches a predetermined value which is sufiicient to overcome the atmospheric pressure and the force of spring 70 and the spool 69 shifts slightly to the right of the compartment 63 to unseat the O-ring 78, and then suddenly snaps to a closed position when the large end surface 81 of the spool 69 is exposed to back pressure of the motor 17. At this time, air flow is shut-off to the motor inlet and air is directed from the chamber 65 through a coupling tube 98 to actuate the marking device 22 housed on top of the motor portion 12 in a manner which wiil be described hereinafter. As will also be described hereinafter, the c ouplin g tube 98 may be connected to a marking device 22 mounted rearwardiy of the handle portion 13 or mounted remotely from the nut runner 10.

Upon releasing the lever 50, the valve spool 40 returns to a normally closed position, permitting the spool 69 to return to its normally open position under the force of spring 70 and in readiness for the next operating cycle.

It should be noted that the nut runner has been described in detail but only for purpose of illustration and other mechanisms which generate a signal of any kind after a predetermined torque has been applied to a retatable fastening member may be used in conjunction with the present invention to mark the rotatable fastening member.

Referring now to FIGS. 5-9, there is illustrated the preferred marking device 22 particularly adapted for use in conjunction with the nut runner 10. The marking device 22 comprises cylindrical housing portions 102,

184, and and a rectangularly shaped end cover 112 secured to one another by screws 113 (FIGS. 7 and 8) extending through the cover 112, housing portions 104, 105 and into threaded bores 196 within the housing portion 102. The housing portion 104 has a cupshaped bore 114 opening to the inner face 115 of the housing portion 105 and supports a piston for sliding reciprocal movement toward and away from the housing portion 102. The housing portion 102 has a longitudinally disposed bore axially aligned with the cup-shaped bore 114 and slidably receiving a piston extension 128 extending from one surface of the piston 120.

The longitudinal bore 130 of the housing portion 102 communicates with a decreased diameter bore 132 (FIGS. 7 and 8) which forms an inlet 134 of a feed passage 136, the outlet of which terminates at an ink coupling tube 138 (FIG. 5) which is mounted to the top of the front portion 14 of the nut runner 10. The coupling tube 138 extends through an axial bore 139 (FlG. l) of the hollow spindle 15 and terminates in a nozzle 14] through which the marking agent is ejected. Referring again to F168. 7 and 8, downstream of the inlet 134 the feed passage 136 forms a valve seat 140 on which a floating spherically-shaped valve member 144 is normally seated. The valve member 144 is in an enlarged chamber 145 axially aligned with the bore 132 and opens into the ink coupling tube 138 through a restricted passageway 137 that forms the outlet of the feed passage 136. The restricted passageway 137 is formed in a threaded member 147 which serves to connect the ink coupling tube 138 to the marking device 22 and which provides a guide for a coil spring 150 having one end bearing against the member 147 and its other end acting against the valve member 144 to norrnally seat the same on valve seat 140 to close communication between the bore 232 and the restricted passageway 137. The valve member 144 is movable between an upstream position where it is seated on the valve seat 140 under the force of the spring 150 to close communication between the feed passage inlet 134 and that portion of the feed passage 136 downstream of the valve seat 140 and an open position in which the valve member 144 is unseated to permit a marking agent to be ejected externally of the marking device by means of the restricted passageway 137 to the ink coupling tube 138, whereby the ejected marking agent is directed through the hollow portion of the spindle 15 to mark the top of the engaged fastening member (FIG. 1). The valve member 144 is unaeated when pressure acts on the same in a manner which will be described in greater detail hereinafter.

Still referring to FIGS. 7-8, a portion of the longitudinal bore 130 of the marking device 22 adjacent the inlet 134 of the feed passage 136 forms a reservoir 152 for containing a quantity of the fluid marking agent. The fluid marking agent within the reservoir 152 is replenished by an external reservoir (not shown) through inlet 156 and a hose 157 (FIGS. 1 and 2).

The piston extension 128 has an enlarged section 158 which slidably engages the bore 130 and is reciprocated by the piston 120 in response to the selective pressurization of chambers 159 and 161 formed on the opposite sides of the piston 120. The projecting end of the piston extension 128 forms a pumping element 160 which is movable between a retracted position as illustrated in FIGS. 5 and 7, wherein it is spaced from the inlet 134 and the feed passage 136 and fluid within the reservoir 152 is freely communicable to the feed passage 136, and an extended position illustrated in FIGS. 6 and 8 in which the pumping element 160 enters the feed passage inlet 134 to close communication between the feed passage 136 and the reservoir 152 separating a slug of the fluid marking agent within the feed passage 136 from the reservoir 152. The pumping element 160 is of a cylindrical shape complementary to the shape of the bore 132 and so sized that when the element 160 engages the bore 132 there is a fluid seal between the outer periphery of the pumping element 160 and the inner surface of the bore 132 so that the fluid trapped within the feed passage 136 will not leak back into the reservoir 152.

As the pumping element 160 is stroked to its ex tended position as will be described hereinafter, it will raise the pressure of the trapped fluid within the feed passage 136 so as to generate a force of sufficient magnitude to move the valve member 144 off the seat 140 against the bias of the spring 150. The charge of marking fluid is then delivered under pressure past the valve member 144, through the passageway 137 externally of the marking device 122, through the ink coupling tube 138, the hollow spindle 15 and to the engaged fastening member to mark the same. As the pumping element 160 starts to return to its retracted position, the spring 150 acts against the valve member 144 to cause the same to again engage the seat 140. As the valve member 144 seats, a vacuum is created in the pump chamber 136 and as retraction of the pumping element 1611 continues communication between the feed passage inlet 134 and the reservoir 152 is open and the amount of fluid ejected from the marking device 22 is replenished therein. The seated valve member 144 prevents the passage of the fluid marking agent from the feed passage 136 until the pumping element 160 is again shifted to its extended position.

Reciprocal movement of the piston 120 is produced by selectively pressurizing the chambers 159 and 161 on the opposite side of the piston 120 by means of a shuttle valve 162, best seen in FIGS. and 6. The valve 162 comprises a spool 164 slidably mounted in a bore 166 formed within the cover 112. The spool 164 has a plurality of longitudinally spaced lands 168, 170 and 172 separated by annular spaces 174 and 176 defined by the interior of the bore 166 and the outer surface of the spool 164. The annular space 176 between lands 170 and 172 communicates with one end of the bore 166 through a T-shaped internal passageway 178, said one end of the bore 166 being vented to atmosphere through an aperture 180 extending through a plug member 182 that threadedly engages the cover 112 in axial alignment with the bore 166.

A source of fluid pressure, which in the present embodiment is the air supply utilized to actuate the nut runner 10, is communicated to a port 184 (FIGS. 7, 8 and 9) at the top of the cover 112 by means of an air supply tube 186 and is so disposed that pressurized air is normally fed to the annular space 174 between the lands 168 and 170. Movement of the spool 164 along the axis of the bore 166 permits communciation between the annular space 174 in one position (FIG. 6) and a port 188 connected to the chamber 161 through drilled passageways T91) in the housing portion 105, and in a second position with a port 192 that is connected to the chamber 159 through drilled passageways 194 and 196 in the housing portions and 104, respectively. A spring 198 carried by the plug member 182 normally biases the spool 164 to the position illustrated in FIGS. 5 and 9 wherein the annular space 174 normally communicates with the inlet port 192 and passages 195 and 196 so as to direct air under pressure to the chamber 159 to generate a force on the piston to move the piston rightwardly and maintain the same in the position shown in FIGS. 5 and 7. As best seen in FIGS. 5 and 6, the end of the bore 166 opposite the spring 198 is threaded to receive a fitting 200 which is connected to the tube 98 leading from the endextension 62 of the shut-off control valve 56 within the nut manner 10.

It can thus be seen that when pressure from the shutoff valve 56 is exhausted through the end extension 62 to the end of the bore 166, pressure will act against the spool face 202 to shift the spool 164 downwardly against the bias of the spring 198 to the position illustrated in FIG. 6, whereby pressurized air is communicated from the annular space 174 through the port 188 and passages 189 to the chamber 161, generating a force against the piston 120 to move the same leftwardly to the extended position shown in FIGS. 6 and 8 to achieve the aforementioned pumping action by the pumping element 160. As the piston moves leftwardly to an extended position, the air within the chamber 159 is exhausted through the passages 194, 196, the port 192, the T-shaped passage 178 and vent aperture 180. As long as the lever 50 is held down and pressurized air is directed from the extension end 62 of the shut-off valve 56 to the cover 112 the spool 164 will be held in the position shown in FIGS. 6 and 8 and pressure will be directed against the piston 120 to maintain the same in its extended position; however, only one slug of the fluid marking agent will be ejected to mark the fastening member.

As soon as the lever 50 is released, the pressure on the spool face 202 of the valve spool 164 will be relieved, whereupon the spring 198 will shift the spool 164 upwardly to the position shown in FIG. 5, at the same time closing off the communication between the annular space 174 and the port 188, while opening up communication between the annular space 174 and the port 192, thereby directing pressurized air to the chamber 159 while the chamber 161 is exhausted through the passage 189, the port 188 and the vent aperture as the land 178 traverses the port 188. The pressurized air communicated to the chamber 159 generates a force against the piston 120 to move the piston 120 back to its retracted position shown in FIGS. 5 and 7, wherein fluid communication between the feed passage inlet 134 and the reservoir 152 is again opened and the unit is in position to eject another slug of the fluid marking agent to mark the next fastening member when a predetermined torque has been applied thereto.

In operation, the nut runner 10 is actuated by depressing the lever 50 whereby pressurized air is communicated to the motor 17, which in turn drives the rotating spindle 15 to apply a predetermined amount of torque to the nut, bolt or the like that is engaged by the socket 16. After the predetermined amount of torque has been applied to the fastening member, a pressure signal in the form of pressurized air is emitted from the shut-off valve 56 and is communicated to the end of the spool 164 in the cover 112. The pressurized air acts against the spool 164 to move the same into the position illustrated in FIG. 6, thereby fluidly connecting the high pressure air from air supply tube 186 to the chamber 16], generating a force against the piston 120 to shift the piston lcftwardly, and thus the pumping element 160 to its extended position. When the pumping element 160 is so driven, the same enters the feed passage bore 132 to close communication between the feed passage inlet 134 and the reservoir 152, thereby trapping a charge of the fluid marking agent therein. As the pumping element 160 traverses the bore 132 toward the end of its stroke (which is determined by the engagement of an enlarged portion 204 of the piston 120 with the blind end of the cup-shaped bore 114 of the housing portion 104), the pressure of the fluid within the bore 132 is raised to a sufficient level to move the valve member 144 off the seat 140 against the bias of the spring 150, whereby fluid is discharged from the marking device 22 through the ink coupling tube 138 to mark the engaged fastening member. The discharge end of the ink tube 138 is reduced in crosssection to form a small orifice which retains a solid ink bank in the tube and gives good direction to the ink jet action to mark the device. A vacuum created upstream in the tube 138 retains the ink within the tube.

When the lever 50 is released and the air pressure being directed against the spool face 202 is relieved, the Spring 198 will return the spool 164 to the position illustrated in FIG. 5, thereby directing pressure fluid to the chamber 159 while venting the chamber 161, thereby generating a force against the piston 120 to move the same rightwardly. With the pumping element 160 in its fully retracted position as illustrated in FIG. 5, fluid communication between the reservoir 152 and the inlet 134 of the feed passage 136 is again opened and the marking device is ready to commence another stroke to eject the fluid marking agent to mark the engaged fastening member after the predetermined torque is delivered.

Referring to FIG. 10 of the drawings, a modification of the marking device 22 is illustrated with the coupling tube 138 mounted to the outer surface of the front por tion 14 of the nut runner 10 adjacent the spindle 15, rather than extending into the spindle as illustrated in FIG. 1, such that the marking agent ejected from the marking device 22 will mark the article or workpiece to which the fastening member is being attached rather than the fastening member itself when a predetermined torque is delivered to the fastening member. As illustrated in FIG. 10, the coupling tube 138 is fastened to one side of the front portion 14 of the nut runner 10 by any suitable means, as for example a tape 206.

In P16. 11 the coupling tube 138 of the marking device 22 is shown as being mounted to the front portion 214 of a pneumatic, in-line nut runner 216 by means of the tape 206 and enables the marking device to function in an identical manner as heretofore described, in that a marking agent is ejected through the coupling tube 138 to mark a workpiece or other article to which the fastening member has been secured with the marking device 22 being actuated by a fluid signal generated by the nut runner 10 (or 216) and as indicated hereinbefore, such a signal may be in the form of a fluid pressure, an electrical or a mechanical signal.

FIG. 12 illustrates the marking device 22 as being rcmotely mounted from the nut runner 10 and adapted to mark a workpiece or article 218 when a predetermined torque has been delivered to a fastening member 219 that is secured to the workpiece 218. The marking device 22 is illustrated as being mounted on a support base 220 and is so positioned that a charge of marking fluid will be delivered under pressure through the passageway 137 or any other small orifice member and externally thereof to mark a portion of the workpiece 218 which is spaced a relatively short distance from the marking device 22. The marking device 22 illustrated in FIG. 12 is identical to the marking device 22 described heretofore with the supply tube 186 being coupled to a source of pressure, the hose 157 communicating with an external ink reservoir (not shown), and the coupling tube 98 being adapted to direct air from the chamber 65 to actuate the marking device 22 in the manner described hereinbefore.

Referring now to FIGS. 13-19, and in particular FIGS. 13, 14 and 19, a modification of the marking device 22 is illustrated in the form of a marking device assembly 250 adapted to be coupled to the air inlet of the nut runner 10. The marking device assembly 250 comprises an air hose coupling member 252 having a longitudinally disposed bore 254 for communicating pressurized air between the hose 23 and the air inlet of the nut runner 10. The opposite ends of the coupling member 252 are respectively connected to the air inlet of the nut runner 10 and the air hose 23 by conventional air fittings 253 and 255.

As can best be seen in FIGS. 13 and 19, the coupling member 252 is provided with an upper annular recess 256 on which a marking device 300 is seated and secured by screws 258 extending radially upwardly through the wall of the coupling member 252 and threadingly engaging bores 260 in the underside of the marking device 300. Access to the screws may be had through diametrically opposed bores 262 in the lower portion of the coupling member 252 which, in turn, are closed by plug members 264 as shown in FIG. 13.

Referring to FIGS. 15, 16, and 17, the marking device 300 is illustrated as comprising six axially aligned cylindrically shaped housing portions, including a pumping portion 302, a bypass vent plate 303, a piston drive portion 304, a porting plate 305, a valve body portion 306 and an end cover 308, all of which are secured to one another by screws 312 extending through the cover 308, valve body portion 306, porting plate 305, piston drive portion 304, bypass vent plate 303 and into threaded bores (unnumbered) within the pumping portion 302. The drive portion 304 has a cupshaped bore 314 opening to the inner face 315 of the porting plate 365 and supports a piston 320 for sliding reciprocable movement toward and away from the pumping portion 302. The pumping portion 302, the bypass vent plate 303 and the adjacent face of the piston drive portion 304 have an axially aligned bore 330 which axially aligned with the cup-shaped bore 314 and slidably receives a piston extension 328 extending from one surface of the piston 320. The faces of the pumping portion 302 and the piston drive portion 304 adjacent the bypass vent plate 303 are each provided with an annular recess 331 to respectively accommodate a Teflon G-ringifi and an elastomer D-ring 325 for a purpose to be described hereinafter. The diametrical clearance between the piston extension 328 and that portion of the bore 330 associated with the bypass vent plate 303 is very small so as to provide a wiping action of the picton extension 328 as the same is reciprocated.

As viewed in FIGS. 15 and 16, that portion of the longitudinal bore 330 within the pumping portion 302 forms a feed passage 336, the outlet of which terminates at the ink coupling tube 138. The opposite end of the coupling tube I38 may be mounted in any of the configurations described hcreinbefore with respect to the embodiments disclosed in FIGS. 1, l0, l1 and 12. Downstream from the piston extension 328, the feed passage 336 forms a valve seat 340 on which a truncated shape valve member 344 is normally seated (FIG. 17). The valve member 344 is loosely slidably mounted in a fitting 345, the inner end of which forms an enlarged chamber 347 (FIG. 15) which communicates with the feed passage 336 when the valve member 344 is unseated in a manner which will be described hereinafter. The diametrical clearance between the valve member 344 and the fitting 345 is sufficiently large to communicate the enlarged chamber 347 with the interior of the fitting 345 which, in turn, communicates with the coupling tube 138 through a restricted passage 35] in a manner similar to that described in the embodiments of FIGS. l9. The fitting 345, in addition to connecting the ink coupling tube 138 to the marking device 300, provides a guide for a coil spring 350 having one end bearing against the fitting 345, while its other end acts against the valve member 344 to normally seat the same on the valve seat 340 (FIG. 17) to close communication between the feed passage 336 and the restricted passageway 351.

The valve member 344 is movable between an upstream position wherein it is seated on the valve seat 340 under the force of the spring 350 to close communication between the feed passage 336 and that portion of the feed passage 336 downstream of the valve seat 340 and an open position in which the valve member 344 is unseated to permit a fluid marking agent to be ejected externally of the marking device 300 around the valve member 344, through the restricted passageway 351 and into the ink coupling tube 138, whereby the ejected marking agent is directed to mark the top of the engaged fastening member or the article to which the fastening member is secured in the same manner as described in the embodiments illustrated in FIGS. 1-l2. The valve member 344 is unseated when pressure acts on the same in a manner which will be described in greater detail hereinafter.

Still referring to FIGS. 13-19, and particularly to FIGS. 15, 16 and 17, a portion of the longitudinal bore 330 of the marking device 300 communicates with radially disposed passageways 352, each of which terminates at a threaded bore 353. One of the bores 353 is adapted to receive a fitting 354 to connect the feed passage 336 to an external reservoir (not shown) by means of an ink supply hose 357 (FIG. 14), while the opposite threaded bore 353 is closed by plug member 355 (FIG. 14). Thus the user is provided with convenient means for coupling the ink supply hose 357 to the opposite side of the marking device 300 so as to more easily accommodate various mounting configurations and applications which may be encountered in using the marking device 300.

The piston extension 328 is reciprocated by the piston 320 in response to the selective pressurization of chambers 359 and 361 formed in the opposite side of the piston 320 within the drive portion 304. The projecting end of the piston extension 328 forms the pumping portion of the marking device and is movable between a retracted position illustrated in FIG. 17, wherein the end of the piston extension 328 is spaced from the radially extending passages 325 such that fluid from the external reservoir is freely communicated to the feed passage 336, and an extended position illustrated in FIGS. 15 and 16 in which the projecting end of the piston extension 328 enters the feed passage 336 to close communication between the feed passage 336 and the radially extending passages 352, thus separating a slug of the fluid marking agent within the feed passage 336 from the external reservoir.

The end of the piston extension 328 is of a cylindrical shape complementary to the shape of the feed passage 326 and is so sized that when the piston extension 328 is slidably reciprocated within the feed passage 336 there is a fluid seal between the outer periphery of the piston extension 328 and the surface of the feed passage 336 so that fluid trapped within the feed passage 336 will not leak back into the external reservoir.

As the end of the piston extension 328 is stroked to its extended position, as will be described hereinafter, it will raise the pressure of the trapped fluid within the feed passage 336 so as to generate a force of sufficient magnitude to move the valve member 344 off the seat 340 against the bias of the spring 350. The charge of marking fluid within the feed passage 336 is then delivered under pressure past the valve member 344, through the passageway 35] and externally of the marking device 300, and through the ink coupling tube 138 to mark the engaged fastening member as described hereinbefore with respect to the embodiments disclosed in FIGS. 1l2.

As the piston extension 328 returns to its retracted position, the spring 350 acts against the valve member 344 to cause the same to again engage the valve seat 340. As the valve member 344 seats, a vacuum is created in the feed passage chamber 336 and as retraction of the piston extension 328 continues, communication between the feed passage 336 and the external reservoir is opened and the amount of fluid ejected from the marking device 300 is replenished within the feed passage. The seated valve member 144 prevents the passage of the fluid marking agent from the feed passage 336 until the piston extension 328 is again shifted to its extended position.

Still referring to FIGS. 15-17, it can be seen that reciprocal movement of the piston 320 is produced by selectively pressurizing the chambers 359 and 361 on the opposite sides of the piston 320. This is accomplished by means ofa shuttle valve 326 housed within the valve body portion 306. The valve 362 comprises a spool 364 slidably mounted in a bore 366, the bore extending completely through the valve body portion 306 and opening to the adjacent inner face of the porting plate 305 and end cover 308. The spool 364 has a plurality of longitudinally spaced lands 368, 370 and 372 separated by annular spaces 374 and 376 defined by the interior of the bore 366 and the outer surface of the spool 364. The annular space 374 between the lands 370 and 372 communicates with the inner end of the bore 366 through a T-shaped internal passageway 378 within the spool. The inner end of the bore 366 is, in turn, vented to atmosphere through an aperture 380 extending through the end cover 308.

A source of fluid pressure, which in the present embodiment is the air supply from the hose 23, is communicated to a passage 384 (FIGS. 16 and 18) through a port 385. The passage 384 extends through the wall of the coupling member 252 and is so disposed that pressurized air from the port 385 is normally communicated to the annular space 374 between the lands 368 and 370.

Movement of the spool 364 along the longitudinal axis of the bore 366 to the position shown in FIGS. 15 and I6 permits communication between the annular space 374 with a port 388 (H6. 15) which is connected to the chamber 361 through longitudinally drill passageways 390 and 39! respectively in the valve body portion 306 and the porting plate 305. Movement of the spool 364 to a second position as shown in FIG. 1? permits communication of the annular space 374 with a port 392 (FIG. 16) that is connected to the chamber I59 through drill passageways 394, 395 and 396 respectively in the valve body portion 306, porting plate 305 and the piston drive portion 304. A spring 398 disposed between the spool 364 and a recess 399 formed on the inner face of the end cover 308 normally biases the spool 364 to the position illustrated in FIG. 17 wherein the annular space 374 normally connects the ports 392 and 385 so as to direct air under pressure to the chamber 359 to generate a force on the piston 320 to move the piston rightwardly and maintain the piston 320 in the position shown in FIG. 17.

As can best be seen in FIGS. 14 and 15, the valve body portion 306 has a threaded connection port 401 for receiving a fitting 400 which is in turn connected to the coupling tube 98 leading from the end extension 62 to shut-off control valve 56 within a nut runner as hereinbefore described. The inner end of the bore 366, that is the end between the porting plate 305 and the inner end 402 of the spool 364, is in fluid communication with the fitting 400 through a passageway 403 disposed in the valve body portion 306and the porting plate 305.

It can thus be seen that when pressure from the valve 56 in the nut runner 10 is exhausted through the end extension 62 to the inner end of the bore 366 through passageway 403, pressure will act against the spool face 402 to shift the spool 364 rightwardly, as viewed in H08. and I6, against the bias of the spring 398 to the position illustrated in FIGS. 15 and 16, whereby air pressure is communicated through the annular space 374 from the port 388 to the chamber 361 to generate a force against the piston 320 to move the same leftwardly and to the extended position shown in FIGS. 15 and 16 to achieve the aforementioned pumping action of the piston extension 328. As the piston 320 moves leftwardly to the extended position, the air within the chamber 359 is exhausted through the passageways 394, 395 and 396, the port 392, the T- shaped passage 378 and the vent aperture 380.

As long as the lever 50 of the nut runner 10 is held down and pressurized air is directed from the extension 62 from the shut-off valve 56 to the inner end 402 of the spool 364, the same will be held in the position shown in FIGS. 15 and i6 and pressure will be directed against the piston 320 to maintain the same in the extended position. However, only one slug of the fluid marking agent will be ejected to mark the fastening member or the article to which the fastening member is secured, depending upon the specific application and embodiment used as described hereinbefore in FIGS. I42.

As soon as the lever 50 of the nut runner 10 is released. the pressure on the inner end 402 of the spool 364 will be relieved. whereupon the spring 398 will shift the spool 364 leftwardly to the position shown in FIG. 17, at the same time closing off communication between the annular space 374 and the port 388, while opening up communication between the annular recess space 374 and the port 392, thereby directing pressurized air from the air hose 23 to the chamber 359, while the chamber 361 is exhausted through the port 388 and the aperture 380. Pressurized air communicated to the chamber 359 generates a force against the piston 320 to move the piston 320 back to its retracted position as shown in FlG. 17 wherein fluid communication between the feed passage 336 and the external reservoir is again open and the unit is in position to eject another slug of the fluid marking agent to mark the next fastening member when a predetermined torque has been applied thereto as described hereinbefore. The O-rings 333 prevent the passage of air from the chamber 359 to the ink supply and vice versa, while a venting passage 410 in the vent plate permits any such leakage to vent to the atmosphere.

In operation, the nut runner 10 is actuated by depressing the lever 50, whereby pressurized air is communicated to the motor 17 which, in turn, drives the spindle 15 to apply a predetermined amount of torque to the nut, bolt or other fastening member that is en gaged by the socket 16. After a predetermined amount of torque has been applied to the fastening member, a signal in the form of pressurized air is emitted from the shut-off valve 56 and communicated to the inner end 402 of spool 364. The pressurized air acts against the spool 364 to move the same to the position illustrated in FIGS. 15 and 16, thereby fluidly connecting the high pressure air from the air supply hose 23 to the chamber 361, generating a force against the piston 320 to shift the piston leftwardly and thus the piston extension 328 to its extended position. When the piston extension 328 is so driven, it enters the feed passage 336 to close off communication between the passage 336 and the radially extending passageways 352 communicating with the external reservoir. thereby trapping a charge of the fluid marking agent within the feed passage 336. 7

As the extension member 328 traverses the feed passage 336 toward the end of its stroke {which is determined by the engagement of an enlarged portion 404 of the piston 320 with the blind end of the cup-shaped bore 314) the pressure of the fluid within the feed passage 336 is raised to a sufficient level to move the valve member 344 off the seat 340 against the bias of the spring 350. Fluid is thereby discharged from the marking device 300 through the ink coupling tube 138 and to the interior of the spindle 15 to mark the engaged fastening member or is discharged to the external mounting assembly illustrated in FIGS. l0 and 11 to mark the article or workpiece to which the fastening member is to be secured,

when the lever 50 is released and the air pressure being directed against the inner end 402 of spool 364 is relieved, the spring 398 will return the spool 364 to the position illustrated in FIG. 17, thereby venting the chamber 361 while directing pressure fluid to the chamber 359, generating a force against the piston 320 to move the same rightwardly. With the piston extension 328 in its fully retracted position as illustrated in FIG. 17, fluid communication between the external reservoir and the feed passageway 336 is again open and the marking device is ready to commence another stroke to eject the fluid marking agent to mark the engaged fastening member or the workpiece carrying the fastening member when a predetermined torque has been delivered to the fastening member.

It can thus be seen that the present invention has provided a marking device for a torque applying tool, such as a nut runner, for automatically placing a marking agent on a rotatable fastening member or a workpiece engaged by the fastening member to indicate the completed application of a preselected torque to the fastening member, and which fastening member cannot be so marked until a predetermined torque has been reached.

The invention can take many forms and can be used in combination with any type ofnut runner which will generate some type of signal when the predetermined torque has been achieved. While in the disclosed embodiments a pneumatically driven nut runner has been described and thus the signal indicating completion of the predetermined torque is in the form of a fluid signal. it is apparent that with appropriate modifications the present invention could be used with a nut runner which generates a mechanical or electrical signal when the predetermined torque has been achieved.

What is claimed is as follows:

1. A torque applying tool comprising:

a housing;

a hollow work spindle rotatably mounted in said housing and adapted at one end thereof to engage a rotatable fastening member and deliver a torque thereto;

a fluid motor operatively coupled to said spindle for rotating same;

pressure fluid means for driving said fluid motor for delivering a predetermined torque to said spindle and thus to said engaged fastening member;

means for providing a pressure fluid signal indicative of said predetermined torque having been delivered;

a marking device carried by said tool and adapted to forcibly eject a fluid marking agent for marking said rotatable fastening member when said predetermined torque has been delivered;

said marking device comprising a second housing having a reservoir for said fluid marking agent; a feed passage having an inlet in communication with said reservoir and an outlet in communication with the other end of said hollow work spindle, said fluid marking agent being adapted to be forcibly ejected from said housing outlet through said hollow work spindle to mark said rotatable fastening member; means for connecting said outlet to said other end of said hollow work spindle; means for closing communication between said reservoir and said feed passage for separating the fluid in said feed passage from the fluid in said reservoir; and means responsive to said pressure fluid signal for pressurizing said separated fluid in said feed passage to forcibly eject a selected amount of said separated fluid through said feed passage outlet to mark said rotatable fastening member.

2. The torque applying tool defined in claim 1 wherein said means for closing fluid communication between said reservoir and said feed passage means comprises a piston member movably mounted within said reservoir between a first position in which said piston engages the inlet of said feed passage to close the fluid communication between said reservoir and said feed passage, and a second position in which said piston member is spaced from said inlet to permit fluid communication between said reservoir and said feed passage.

3. The torque applying tool defined in claim 1 wherein said means for prcssurizing said fluid in said feed passages comprises:

a chamber;

a piston member movably mounted in said chamber,

a portion of said piston being disposed in said reser voir and movable between a first position in which said piston member portion engages the inlet of said feed passage to close fluid communication between said reservoir and said feed passage to forci bly eject said separated fluid from said feed passage to mark said rotatable fastening member, and a second position in which said piston portion is spaced from said inlet to permit fluid communication between said reservoir and said feed passage;

a source of fluid pressure; and

valve means responsive to said fluid pressure signal to communicate said source of fluid pressure to one side of said piston to move said piston to said first position,

4. The torque applying tool defined in claim 3 wherein said valve means is adapted to communicate said source of fluid pressure to the other side of said piston to move said piston to said second position when said fluid pressure signal is terminated.

5. The torque applying tool defined in claim 3 wherein said valve means comprises a valve spool slidably disposed in a bore in said marking device housing, said bore having spaced ports one of which is in communication with said chamber on one side of said piston, the other port being in communication with said chamber on the other side of said piston, said source of fluid pressure being communicated to said bore, said spool having means for connecting said source of fluid pressure to said one port for moving said piston to said first position and for exhausting said chamber on said one side of said piston when said piston is moved to said second position; and means normally biasing said spool to a positon causing said piston to be moved to said first position.

6. The torque applying tool defined in claim 5 wherein said spool means is adapted to connect said source of pressure to said other side of said piston to move said piston to said second position when said one side of said piston is exhausted.

7. The torque applying device defined in claim 1 including check valve means in said feed passage downstream from said feed passage inlet for preventing the passage of said fluid marking agent until the pressure in said feed passage exceeds a preselected value.

a a s w UNITED STATES PAII'IN'I OFFICE (11*) RT! FH ZA'llfi H" (10R R M I'IIUN 3,802,301 April 9, 1974 Patent No. Dated Rudolph 6. Peterson Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 52, after "Valve" cancel "spool".

Column 7, line 66, "190" should be 189 Column 8,

line 6, "195" should be 194 line 14, "manner" should be runner Column 12, line 3, delete "325" and insert 352 line 51, delete "326" and insert 362 Signed and sealed this 12th day of November 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PQ'WSD uscow-oc wan-poo S GOVEPNIENY PRINTING OFFIC! Bag- 93 0 

1. A torque applying tool comprising: a housing; a hollow work spindle rotatably mounted in said housing and adapted at one end thereof to engage a rotatable fastening member and deliver a torque thereto; a fluid motor operatively coupled to said spindle for rotating same; pressure fluid means for driving said fluid motor for delivering a predetermined torque to said spindle and thus to said engaged fastening member; means for providing a pressure fluid signal indicative of said predetermined torque having been delivered; a marking device carried by said tool and adapted to forcibly eject a fluid marking agent for marking said rotatable fastening member when said predetermined torque has been delivered; said marking device comprising a second housing having a reservoir for said fluid marking agent; a feed passage having an inlet in communication with said reservoir and an outlet in communication with the other end of said hollow work spindle, said fluid marking agent being adapted to be forcibly ejected from said housing outlet through said hollow work spindle to mark said rotatable fastening member; means for connecting said outlet to said other end of said hollow work spindle; means for closing communication between said reservoir and said feed passage for separating the fluid in said feed passage from the fluid in said reservoir; and means responsive to said pressure fluid signal for pressurizing said separated fluid in said feed passage to forcibly eject a selected amount of said separated fluid through said feed passage outlet to mark said rotatable fastening member.
 2. The torque applying tool defined in claim 1 wherein said means for closing fluid communication between said reservoir and said feed passage means comprises a piston member movably mounted within said reservoir between a first position in which said piston engages the inlet of said feed passage to close the fluid communication between said reservoir and said feed passage, and a second position in which said piston member is spaced from said inlet to permit fluid communication between said reservoir and said feed passage.
 3. The torque applying tool defined in claim 1 wherein said means for pressurizing said fluid in said feed passages comprises: a chamber; a piston member movably mounted in said chamber, a portion of said piston being disposed in said reservoir and movable between a first position in which said piston member portion engages the inlet of said feed passage to close fluid communication between said reservoir and said feed passage to forcibly eject said separated fluid from said feed passage to mark said rotatable fastening member, and a second position in which said piston portion is spaced from said inlet to permit fluid communication between said reservoir and said feed passage; a source of fluid pressure; and valve means responsive to said fluid pressure signal to communicate said source of fluid pressure to one side of said piston to move said piston to said first position,
 4. The torque applying tool defined in claim 3 wherein said valve means is adapted to communicate said source of fluid pressure to the other side of said piston to move said piston to said second position when said fluid pressure signal is terminated.
 5. The torque applying tool defined in claim 3 wherein said valve means comprises a valve spool slidably disposed in a bore in said marking device housing, said bore having spaced ports one of which is in communication with said chamber on one side of said piston, the other port being in communication with said chamber on the other side of said piston, said source of fluid pressure being communicated to said bore, said spool having means for connecting said source of fluid pressure to said one port for moving said piston to said first position and for exhausting said chamber on said one side of said piston when said piston is moved to said second position; and means normally biasing said spool to a position causing said piston to be moved to said first position.
 6. The torque applying tool defined in claim 5 wherein said spool means is adapted to connect said source of pressure to said other side of said piston to move said piston to said second position when said one side of said piston is exhausted.
 7. The torque applying device defined in claim 1 including check valve means in said feed passage downstream from said feed passage inlet for preventing the passage of said fluid marking agent until the pressure in said feed passage exceeds a preselected value. 